My brother, Randy, maintains that Lost Mine Trail gives you the most "bang
for the buck" in terms of scenery versus effort expended, and, after taking
the hike myself, I can't argue
with him. The trail begins in Green Gulch in the high Chisos Mountains at a
well-marked trailhead and is relatively effortless until you get toward the end,
where you do have to expend a bit of effort in elevation gain. However, all
along the way you are offered dramatic views of the Chisos Mountains.

You can look down two canyons as you get toward the end of the trail. The
view below, looking east, is of Pine Canyon, which cuts through the heart of
the Pine Canyon Caldera, a small
caldera, that erupted around
33 million years ago. (A caldera is formed when lava exits a volcanic mountain,
removing the means of the mountain's support. The mountain collapses, resulting
in an eruption of
pyroclastic
volcanism.) The result of this eruption was the deposition of glowing
clouds of ash and debris called
ignimbrite, forming the
Pine Canyon
Rhyolite, formerly known
as the Brown Rhyolite. (The nomenclature of the rock units in the Chisos
Mountains has undergone a recent change to correspond to the latest research.
Some units with the same name and similar properties and age in different parts
of the park have been shown not to be the same units.) Rhyolite is a volcanic
rock very high in silicon and
oxygen and whose deposition tends to be accompanied by violent eruptions due
to the high viscosity of the rhyolitic magma, which can trap volcanic gases
until the pressure builds up to explosive proportions.

Along the trail you come across the volcanics of the Chisos Group of rocks
(formerly known as the Chisos Formation). The image below is of a layer of
Chisos volcanic
ash along the side of
the trail. The Chisos Group was deposited in various eruptions and sedimentary
episodes beginning around 47 million years ago, prior to the Pine Canyon
Caldera eruptions.

The Agave americana (century plants) were gorgeous along the trail.
Below, my brother, Randy, is taking
a picture of a particularly nice specimen with beautiful Juniper Canyon in
the background. The higher ridges on the right are composed of the rhyolitic
Boot Rock Member of the South Rim Formation (formerly, the Lost Mine Rhyolite).
The lower ridges mark the outcrop of an
igneous intrusion,
a body of magma that pushed its way upward into the surrounding rock.

Here is the picture Randy took. The blooming Agave on this hike were
spectacular. It could be that the exceptionally rainy spring attributed to
their beauty (but I'm no botanist).

The following picture is a view toward Casa Grande Peak, which
is topped by the very resistant Emory Peak Rhyolite, formerly known as the
Burro Mesa Rhyolite. (The rhyolite on
Burro Mesa has different origin.)
My brother, Randy, formerly known as Alan, pauses to take in the view.
(Actually, Randy did not have to change his name to suite the new nomenclature.
However, in another sense this is true. In England "randy" has a bit of a vulgar
meaning, so when we visited him there we would always refer to him by his first
name, Alan, in public.)

The Emory Peak Rhyolite also forms the "caprock" on
Emory and Lost Mine Peaks. Emory Peak is the highest point in the park at 7835
feet elevation. To the left of Casa Grande is the northern shoulder of Toll
Mountain, on top of which is found the Boot Rock Member.
Stratigraphically, the
Emory Peak Rhyolite lies on top of the Boot Rock Member which, in turn,
overlies the Pine Canyon Rhyolite. All these are
members of the
South Rim
Formation, which was
erupted between 33 and 32 million years ago. Note the Agave just beyond
Randy and the Sotol to his right, both with tall blooms.

Juniper Canyon was particulary gorgeous this trip (June, 2007) due to the
wet spring. Canyons such as this widen as
mass wasting, processes
(for example, rock falls and soil creep) erode away the slopes. The debris from
these processes are moved downstream during the infrequent desert downbursts,
deepening the canyon.

Below is a view back toward
The Basin. Casa Grande is on the
left. In the distance is The Window, a gap between Amon Carter Peak on the left
and Vernon Bailey Peak on the right. The Window is the only outlet for water
from The Basin.

In this view of Juniper Canyon you see a linear igneous intrusion
associated with the formation of the Pine Canyon Caldera. It is continued on
the other side of the canyon where it forms Hayes Ridge. Boot Canyon descends
into Juniper Canyon between this intrusion and the cliffs in the right middle
distance.

This is the end of the trail. It terminates at an east-west trending
igneous dike, a
sheet-shaped igneous intrusion that cuts across pre-existing geologic
structure. Here you see brother Randolph with his back on the dike and his
feet on what was previously known as the Wasp Spring Flow Breccia (now a unit
of the Boot Rock Member of the South Rim Formation). The
steep dropoff behind him is apparently the result of a north-south trending
fault. Faults are often zones of weakness in the rock where erosion can be
enhanced. As indicated in the image, Lost Mine Peak is to the left and Crown
Mountain is in the distance. The higher elevations of Crown Mountain consist of
the Boot Rock Member (formerly the Wasp Spring Flow Breccia overlain by the
Lost Mine Rhyolite). The
flatiron below Crown
Mountain appears to be made of Pine Canyon Rhyolite, the original material
erupted from the Pine Canyon caldera mentioned above.

Lost Mine Peak. Legends of a lost mine on the peak are almost certainly
fabrications. Note the grayish rock extending from lower right to upper left
across the face of the mountain. This appears to be another igneous dike.

A closeup of the contact between the "Wasp Spring Flow Breccia" and the
dike at the end of the Lost Mine trail. The fault scarp with a shear dropoff
is on the other side of the backpack.

In this view you are looking almost due south. Elephant Tusk and
Backbone Ridge (just to the right of Elephant Tusk, on the edge of the image)
are in the distance, almost eight miles away. Both are igneous intrusions. The
fault at the end of the trail is marked with the dashed line, and Lost Mine
Peak is off to the left. The Rio Grande, about 5000 feet in elevation below
you and 18 miles distant, is the greenish strip indicated. At this point the
Rio has turned
northward as it rounds its Big Bend. The rocks in the foreground on the lower
right may have been
distorted to their current positions by action along the fault.

Finally, here is the intrepid explorer viewing the horizon for new lands to
conquer. My wife has dubbed this picture "Nerd of the Jungle" and has gleefully
sent it to all her relatives.

Nerd, Nerd, Nerd of the jungle,Mounts the rock with pep.
Nerd, Nerd, Nerd of the jungle,Look out where you step!